Device for axially conveying fluids

ABSTRACT

A device for axially conveying fluids, wherein the conveyor part thereof is entirely magnetically borne and the radial bearing thereof is provided with sufficient rigidity and efficiently dampened, whereby problems encountered when passing through critical speeds and the disadvantageous effects of hydrodynamic and mechanical imbalance of the rotor are avoided. The magnetic bearing is combined with a hydrodynamic bearing.

DESCRIPTION

[0001] The invention relates to a device for axially conveying fluids inaccordance with the generic term of claim 1.

[0002] In particular, less stable multiple-phase fluids which canundergo irreversible changes caused by an energy input, such as in thecase of emulsions and dispersions, can run into unstable ranges in adisadvantageous manner when being conveyed in corresponding devices suchas pumps.

[0003] Blood is a particularly sensitive fluid system. This opaque redbody fluid of the vertebrates circulates in a self-enclosed vesselsystem where rhythmic contractions of the heart press the blood intovarious areas of the organism. In this case, the blood transports therespiratory gases oxygen and carbon dioxide as well as nutrients,metabolic products and endogenous active ingredients. The blood vesselsystem including the heart is hermetically isolated from the environmentso that, in a healthy organism, the blood does not undergo any changes,except for the material exchange with the body cells, when it is pumpedthrough the body by way of the heart.

[0004] It is known that, when blood comes into contact withnon-endogenous materials or as a result of the effect of energy from anexternal source, it has a tendency to hemolysis and clot formation. Clotformation can be fatal for the organism because it can lead to blockagein the extensive branching profile of the vessel system. Hemolysisdescribes the condition where the red blood cells are destroyed withinthe body beyond the physiological dimension.

[0005] The causes for hemolysis can be of a mechanical or metabolicnature. Increased hemolysis causes multiple organ damage and can lead toa person's death.

[0006] On the other hand it is evident that it is possible in principle,under certain prerequisites with reference to constructive aspects, tosupport the pumping capacity of the heart or even to replace the naturalheart with a synthetic one. However, a continuous operation of implantedheart supporting systems or synthetic hearts is presently only possiblewith certain limitations because the interactive effects of theseartificial products with the blood and the entire organism still alwayslead to disadvantageous changes of the blood and the organism.

[0007] In the state of the art, axial blood pumps are known which mainlyconsist of a cylindrical tube in which a conveying part, which isexecuted as a rotor of an externally located motor stator, rotates. Therotor which is provided with a so-called blading, conveys the fluid inan axial direction after it has been made to rotate. The bearing ofthese so-called axial pumps represents a major problem. A purelymechanically bearing is disadvantageous with regard to blood damage andalso the relatively high friction levels. And the magnet bearingvariants as described up to the present have not, in particular, led toany satisfactory solution for the bearing conditions in axial pumps.

[0008] In the WO 00/64030 a device for the protective conveying ofsingle- and multiple phase fluids is described whose conveying part isexclusively magnetically bearing-located. For this purpose, permanentmagnetic bearing elements for the magnet bearing-location as well aspermanent magnetic elements for the functionality as a motor rotor of anelectromotor are preferentially integrated in the conveying part. Theuse of a magnet bearing for the conveying facility as described heremakes it possible to waive bearing elements normally arranged in theflow current of the fluid to be conveyed which lead to dead water zonesand vorticities of the fluid to be conveyed and, subsequently, have anegative influence on the current flow.

[0009] The magnetic bearing described here accommodates both the axialas well as the radial forces. The axial location of the conveying partis actively stabilised whereas the radial bearing of the conveying partis effected exclusively passive by means of the existing permanentmagnets. However, the conveying facility as described has severaldisadvantages.

[0010] The passive magnetic radial bearing is characterised byrelatively low rigidity and dampening where, during the pumping action,problems occur when passing through critical speeds of the rotor and/orthe bearing. Possibly existing hydrodynamic and mechanical imbalance ofthe rotor has serious effects on the function of the pump, particularlywhen used as a blood-conveying facility.

[0011] The invention is based on the task assignment of presenting adevice for the axial conveying of fluids whose conveying part iscompletely magnetically borne and whose radial bearing has sufficientrigidity and effective dampening so that problems encountered whenpassing through critical speeds and the disadvantageous effects ofhydrodynamic and mechanical imbalance of the rotor are avoided.

[0012] The solution for the task assignment is effected with a devicefor axially conveying fluids in accordance with the designating part ofclaim 1.

[0013] Such is the device for axially conveying fluids, consisting of atube-shaped hollow body which conducts the fluid in an essentially axialmanner, in which a magnetically borne conveying part is arranged inaxial alignment with a motor stator located outside of the hollow bodycapable of rotating said conveying part, where the one conveying parthaving a magnetic bearing has rotor blading, wherein the magneticbearing is combined with a hydrodynamic bearing.

[0014] Further advantageous embodiments are stated in the Subclaims.

[0015] The bearing of the conveying part has an actively stabilisingmagnetic axial bearing, a passive magnetic radial bearing and ahydrodynamic radial bearing. The hydrodynamic radial bearing is executedin a further embodiment of the invention as a hollow-cylindrical,rotation-symmetrical back-up ring which is joined to the conveying part.

[0016] On the conveying part, at least one back-up ring is arranged,where the back-up rings are arranged at the beginning of the motor rotorand/or at the end of the motor rotor or between these said positions.

[0017] In a further embodiment of the invention, the axial dimension ofthe back-up ring corresponds, at the maximum, to the axial length of theconveying part, and the axial dimension of the running surface of theback-up ring is smaller than one internal surface of the back-up ring.

[0018] The back-up ring has the same radial dimension as the rotorblading and is joined to it.

[0019] Furthermore as an embodiment, the back-up ring has such a radialdimension (thickness) that it can be provided with a radial profilewhich services the purpose of conditioning the inflow into the rotorblading of the conveying part.

[0020] In a further embodiment, a back-up ring is provided with such anaxial reach that the blading over its entire length is restrictedradially from the back-up ring. The running surface of the back-up ringwhich points against internal side of the tube-shaped hollow body, hasin an advantageous manner a surface coating with emergency runcharacteristics and this coating is, moreover, bio-compatible.

[0021] The internal surface of the back-up ring has, in one execution, aprofile which can favourably influence the current flow properties.

[0022] The execution of the running surface of the back-up ring as onerunning line leads to particularly favourable friction values.

[0023] The major rigidity and dampening of the radial bearing of theconveying part is achieved in such a way that, in addition to a magneticbearing of the conveying part, a hydrodynamic bearing is envisaged. Thehydrodynamic bearing is achieved by at least one hollow-cylindrical,rotation-symmetrical back-up ring which is solidly joined to theconveying part. With a suitable execution of the back-up ring, the rotorreceives major tilting rigidity. Advantageously, this effect is obtainedby a particularly large axial reach of the back-up ring or by thearrangement of at least two back-up rings at one rotor.

[0024] With a large axial reach of the back-up ring and/or extensive orcomplete encapsulation of the blading by means of such a back-up ring,damaging effects of the radial gap occurring at the blade ends areadvantageously avoided.

[0025] The invention is explained in greater detail based on a drawing:

[0026] The Figures show the following:

[0027]FIG. 1: a schematic illustration of an axial section of an axialblood pump with back-up ring;

[0028]FIG. 2: a schematic illustration of an arrangement of a back-upring on the rotor;

[0029]FIG. 3: a schematic illustration of an arrangement of two back-uprings on the rotor;

[0030]FIG. 4: a schematic illustration of an arrangement of a back-upring with profiled internal surface;

[0031]FIG. 5: a schematic illustration of a back-up ring reaching overthe entire rotor, and

[0032]FIG. 6: a schematic illustration of a back-up ring on the rotorwith a running line on the running surface.

[0033] In an exemplary manner, FIG. 1 shows in an axial sectionalillustration the construction of a category-related axial pump with thebearing, according to the invention, of a conveying part 4. In its mainparts, the axial pump consists of a tube-shaped hollow body 1 and a pumpcasing 3 that includes a motor stator 7 and axial stabilisers 6. Thepump casing 3 lies immediately and rotation-symmetrical on thetube-shaped hollow body 1. In the interior of the tube-shaped hollowbody 1, a fluid inlet guide facility 5 and a fluid outlet guide facility5′ are envisaged, between which the conveying part 4, which is rotatedby the motor stator 7, is arranged.

[0034] The conveying part 4 has a magnetic bearing where permanentmagnetic bearing elements 9 and 9 are arranged in the motor rotor 8 andpermanent magnetic bearing elements 10 and 10′ are arranged in the fluidinlet- and fluid outlet guide facilities 5 and 5′. On the motor rotor 8of the conveying part 4, a rotor blading 11 is envisaged which iscombined with a back-up ring. The magnetically bearing-located conveyingpart 4 is rotated by way of the motor stator 7 where, by means of theoppositely located permanent magnetic bearing elements 9, 9′ and 10, 10′in combination with the axial stabilisers 6, the conveying part is keptin a floating state and the back-up ring provides for an additionalhydrodynamic bearing-location of the rotating conveying part 4.

[0035]FIG. 2 shows in a schematic illustration the motor rotor 8 withthe rotor blading 11 in a cut-open tube-shaped hollow body 1. Inaccordance with the invention, the back-up ring here is arranged in theend zone of the motor stator 8. The fluid to be conveyed is movedbetween an internal surface 16 of the back-up ring 13 and the motorrotor 8. A running surface 14 of the back-up ring 13 is moved with aminimum clearance to an internal wall 2 of the tube-shaped hollow body1.

[0036]FIG. 3 shows in schematic illustration an arrangement of twoback-up rings 13 and 13′ at the ends of a motor rotor 8. Theillustration of the tube-shaped hollow body 1 has been left out here.

[0037]FIG. 4 shows a further embodiment, according to the invention, ofthe back-up ring 13. The internal surface 16 of the back-up ring 13shows a profile 15. As can be seen in the sectional illustration of theback-up ring 13, the profile 15 is executed here in a bearing-surfacesimilar form. In this case also, the illustration of the tube-shapedhollow body has been waived.

[0038] In a further embodiment of the invention, as shown in FIG. 5, aback-up ring 13 is arranged without an illustration of the tube-shapedhollow body 1, and this back-up ring covers the entire axial length ofthe motor rotor 8 with its blading 11. The conveying of the fluid isalso effected here between the internal surface 16 of the back-up ring13 and the motor rotor 8.

[0039] In a further embodiment of the invention, a back-up ring is shownin FIG. 6 whose running surface 14 has a raised running line 17 whichfacilitates a minimum clearance combined with a minimum frictionopposite the internal wall 2 of the tube-shaped hollow body 1.

Referenced Parts List

[0040]1 Tube-shaped hollow body

[0041]2 Internal wall

[0042]3 Pump casing

[0043]4 conveying part

[0044]5 Fluid inlet guide facility

[0045]5′ Fluid outlet guide facility

[0046]6 Axial stabiliser

[0047]7 Motor stator

[0048]8 Motor rotor

[0049]9 Permanent magnetic bearing element

[0050]9′ Permanent magnetic bearing element

[0051]10 Permanent magnetic bearing element

[0052]10′ Permanent magnetic bearing element

[0053]11 Rotor blading

[0054]12 Fluid guide blading

[0055]12′ Fluid guide blading

[0056]13 Back-up ring

[0057]13′ Back-up ring

[0058]14 Running surface

[0059]15 Profile

[0060]16 Internal surface

[0061]17 Running line

1. Device for axially conveying fluids, consisting of a tube-shapedhollow body (1) which conducts the fluid in an essentially axial manner,in which a magnetically borne conveying part (4) is arranged in axialalignment with a motor stator (7) located outside of the hollow body (1)capable of rotating said conveying part, where the one conveying part(4) having a magnetic bearing has a rotor blading (11), wherein themagnetic bearing is combined with a hydrodynamic bearing.
 2. Deviceaccording to claim 1, wherein the bearing of the conveying part (4) hasan actively stabilising magnetic axial bearing, a passive magneticradial bearing and a hydrodynamic radial bearing (13).
 3. Deviceaccording to claims 1 or 2, wherein the hydrodynamic radial bearing isexecuted as a hollow-cylindrical, rotation-symmetrical back-up ring (13)which is joined to the conveying part (4).
 4. Device according to one ofthe claims 1 to 3, wherein at least one back-up ring (13) is arranged onthe conveying part (4).
 5. Device according to one of the claims 1 to 4,wherein the back-up rings (13) are arranged at the beginning of themotor rotor (8) and/or at the end of the motor rotor (8) or betweenthese positions as stated.
 6. Device according to one of the claims 1 to5, wherein the axial dimension of the back-up ring (13) corresponds at amaximum to the axial length of the conveying part (4).
 7. Deviceaccording to one of the claims 1 to 6, wherein the axial dimension ofthe running surface (14) of the back-up ring (13) is smaller than theinternal surface (16) of the back-up ring (13).
 8. Device according toone of the claims 1 to 7, wherein the back-up ring (13) has the sameradial dimension as the rotor blading (11).
 9. Device according to oneof the claims 1 to 8, wherein the back-up ring (13) and the rotorblading (11) are joined together.
 10. Device according to one of theclaims 1 to 9, wherein the back-up ring (13) has such a radial dimension(thickness) that it can be provided with a radial profile which servesthe purpose of conditioning of the inflow into the rotor blading (11) ofthe conveying part (4).
 11. Device according to one of the claims 1 to10, wherein a back-up ring (13) exists with such an axial reach that theblading (11) over its entire length is radially restricted from theback-up ring (13).
 12. Device according to one of the claims 1 to 11,wherein the running surface (14) of the back-up ring (13), which pointsagainst the internal side of the tube-shaped hollow body (1), has asurface coating with emergency running properties and which is,moreover, bio-compatible.
 13. Device according to one of the claims 1 to12, wherein the internal surface (16) of the back-up ring (13) has aprofile (15).
 14. Device according to one of the claims 1 to 13, whereinthe running surface (14) of the back-up ring (13) has a running line(17).